Porting D2 code to D1

[Steven Schveighoffer]

"Jason House" wrote
> It may sound backwards, but I think it may be the best way to get things 
> like Tango to move forward to D2.
>
> Tango officially supports D1.  If it were to add D2 support, someone would 
> have to port the D1 code to D2.  Then, with each change, a similar change 
> must occur to the D2 code base.  From a maintenance standpoint, this 
> really shouldn't be acceptable.
>
> Since adding concepts such as const to D1 code in an automated fashion is 
> essentially impossible, it seems the best approach is to convert D2 code 
> into D1 code.  Programatically, it should be pretty easy to remove 
> const-awareness.  That'd allow Tango to convert to D2 once and then (more 
> or less) maintain one code base.
>
> Maybe this would require a few special cases with D1-specific and 
> D2-specific code, but I'd hope that wouldn't be very common.  I guess I 
> have a few questions:
>
> 1. Besides const removal, what else must get done to convert D2 code to D1 
> code?
> 2. How can D version-specific code be mixed into a single code base?
> 3. Any thoughts on how to programatically do all the conversions?
> 4. Would this be enough for D1 library maintainers to move to D2?

As someone who has worked on trying to port Tango to D2 (as recently as last 
week), I believe there is more work to be done on D2 before anything like 
this is considered.

As of now, I have at least one critical bug that must be solved before Tango 
on D2 can be done:

http://d.puremagic.com/issues/show_bug.cgi?id=1644

Unless Tango actually builds on D2, there is no point at looking for ways to 
port changes back to D1 :)

-Steve